In recent years there is a growing concern about the accumulation in the environment of pollutants emitted from the burning of hydrocarbon fuels. One source of pollutants, the internal combustion engine, is of concern. In particular, the diesel engine is the focus of a high degree of concern due to the high level of particulate matter produced by that type of engine. The U.S. Environmental Protection Agency heavy-duty diesel emission regulations require that by the year 1991 the emission of particulate matter must be reduced from 0.60 grams per (brake-horsepower)-hour (g/bhp-hr) to 0.25 g/bhp-hr for trucks and 0.10 g/bhp-hr for urban buses. Heavy-duty trucks must meet the same standard as the 1991 urban bus standard by the year 1994. Although thorough optimization of internal engine components, the application of new component technology such as electronic control and variable geometry turbocharging, and emission after-treatment (particulate traps, catalysts, etc.) might achieve some reduction in emissions, the development of diesel engines capable of utilizing alternative fuels which do not generate the high level of particulate matter generated by diesel fuel is important in achieving these strict emission standards. Promising alternative fuels include methanol and ethanol.
Internal combustion diesel engines configured to run on methanol have problems with plugging and fouling of the fuel injectors and fuel pumps. It has been discovered that plugging and fouling are often caused by deposits found near any fuel-lubricant interface, such as within the body of the fuel injector and in the fuel pressuring pump, if one exists, and also at the fuel injector tip. Those deposits have a significant deleterious effect upon the performance and fuel efficiency of fuel-modified internal combustion engines due to interference with the flow of fuel to the fuel injector tip and distortions in the spray pattern of the fuel emitted from the tip of the fuel injector into the combustion chamber.
At the same time, an engine run on alcohol fuel requires effective rust and corrosion inhibition, since alcohol fuels generate more water, formic acid and formaldehyde than diesel fuel, a combination which is highly corrosive to most metallic engine parts. Corrosion often occurs in combustion chambers, particularly on piston heads, and can also occur on the crankshaft, bearings, and other mechanical components which directly or indirectly come into contact with the fuel or its combustion products. Attempts to avoid the fuel injector fouling problem by reducing the concentration of lubricant additive in the lubricant formulation reduce the level of components which provide the critical rust and corrosion inhibition required by alcohol-powered internal combustion engines.
Reducing the quantity of lubricant additives also prevents formulations from qualifying for use in diesel or gasoline fueled engines, making it necessary to stock a separate formulation for alcohol-powered engines and safeguard against use in the wrong engine.
The present invention is directed to lubricant compositions and concentrates for making them which solve the fuel injector plugging and fouling problem and, at the same time, provide effective rust and corrosion inhibition. These lubricant compositions generally comprise at least one neutral or basic salt of at least one acidic organic compound wherein the metal in said salt is magnesium or barium, or a mixture thereof, and, optionally, at least one hydrocarbyl-substituted ashless dispersant wherein each hydrocarbyl substituent has a number average molecular weight up to about 1500, provided that the amounts of calcium, hydrocarbyl-substituted ashless dispersant in which a hydrocarbyl substituent has a number average molecular weight greater than about 1500, and optionally polymeric viscosity improvers are below certain limits further described below. These lubricants can be formulated to qualify for use in more conventional diesel- and gasoline-powered engines.
The book "Lubricant Additives" by M. W. Ranney, published by Noyes Data Corporation of Parkridge, N.J. (1973), discloses a number of metal salts of various sulfonic and carboxylic acids and of phenols which are useful as detergent/ dispersants in lubricating oil products. The book also entitled "Lubricant Additives" by C. V. Smallheer and R. K. Smith, published by the Lezius-Hiles Co. of Cleveland, Ohio (1967), similarly discloses a number of detergent/ dispersants including sulfonates, phenates and carboxylates which are useful as dispersants.
Novel methods for lubricating sump-lubricated fuel-injected alcohol-powered internal combustion engines which solve the fuel injector plugging and fouling problems and/or provide effective rust and/or corrosion inhibition are also included within the scope of the present invention.